This invention relates to absorbent articles using both cellulosic fiber material and particles of a hydrogel-forming polymeric gelling agent as absorbents. Absorbent articles of this type include disposable diapers, adult incontinence pads and briefs and the like which are required to handle relatively large amounts of discharged body fluids.
Absorbent structures which comprise entangled masses of fibers, i.e., fibrous webs, are well known in the art. Such structures can imbibe liquids, such as discharged body fluids, both by an absorption mechanism wherein fluid is taken up by the fiber material itself and by a wicking mechanism wherein fluid is acquired by, distributed through and stored in the capillary interstices between fibers. One means for improving the absorbency characteristics of such fibrous web structures is to incorporate therein so-called superabsorbent polymers which imbibe fluid to thereby form a swollen hydrogel material. The resulting hydrogel serves to retain fluid such as discharged body liquids within the structure. An absorbent structure of this type wherein hydrogel-forming materials in particulate form are incorporated into fibrous webs is disclosed in Weisman and Goldman; U.S. Pat. No. 4,610,678; issued Sept. 9, 1986.
The improvement in absorbency provided by incorporation of hydrogel-forming absorbent gelling materials has permitted the realization of absorbent articles such as diapers which employ relatively thin absorbent cores and which are, therefore, relatively thin products. Thinner diapers are less bulky to wear and fit better under clothing. They are also more compact in the package, making the diapers easier for the consumer to carry and store. Compactness in packaging also results in reduced distribution costs for the manufacturer and distributor.
In order to realize acceptable thin absorbent articles which retain desirable absorbency characteristics, it is essential that the absorbent core of such articles be of a configuration which tends to maximize the absorbent efficiency of both the fibrous matrix and the polymeric gelling agent material, if any, used therein. One such absorbent core configuration is disclosed in Weisman/Houghton/Gellert; U.S. Pat. No. 4,673,402; issued June 16, 1987. This patent discloses absorbent articles having a dual layer absorbent core. In the dual layer configuration, the core comprises an upper primary layer which is an airlaid web of hydrophilic fiber material, optionally with a small amount of polymeric gelling agent particles admixed therewith. The core also comprises an underlying insert layer which is an airlaid mixture of hydrophilic fiber material and a substantial amount of polymeric gelling agent particles. This insert layer is generally positioned toward the front of the absorbent article such that more than half of the polymeric gelling agent material in the article is found in the front half thereof. Absorbent articles having the particular dual layer configuration of the '402 patent can be prepared in the form of especially thin, highly effective, low leakage diaper products.
Notwithstanding the existence of thin absorbent articles of the type described in the '402 patent, there is a continuing need to identify preferred configurations for absorbent articles which would permit the realization of even thinner products employing less absorbent material therein. Such articles would be even less costly to manufacture and distribute than existing known products. Such products would also find great acceptance among consumers looking for especially thin, better fitting, low leakage products.
Accordingly, it is an object of the present invention to provide improved absorbent articles utilizing a dual layer absorbent core that effectively and efficiently absorbs and stores the wearer's discharged body fluids.
It is a further object of the present invention to provide such improved absorbent articles in the form of very thin, easy to manufacture, compact products using less absorbent material than similar products of the prior art.
It is a further object of the present invention to provide such thin, compact, nonbulky absorbent articles having leakage incidence which is equivalent to or lower than that of existing commercially marketed disposable absorbent products.